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HomePediatrics: General MedicinePediatric Hypertrophic Pyloric Stenosis

Pediatric Hypertrophic Pyloric Stenosis

Practice Essentials

Hypertrophic pyloric stenosis (HPS) causes a functional gastric outlet obstruction as a result of hypertrophy and hyperplasia of the muscular layers of the pylorus. In infants, hypertrophic pyloric stenosis is the most common cause of gastric outlet obstruction and the most common surgical cause of vomiting.

Signs and symptoms

Features of the history in infants with hypertrophic pyloric stenosis are as follows:

Typical presentation is onset of initially nonbloody, usually nonbilious vomiting at 4-8 weeks of age

Although vomiting may initially be infrequent, over several days it becomes more predictable, occurring at nearly every feeding

Vomiting intensity also increases until pathognomonic projectile vomiting ensues

Slight hematemesis of either bright-red flecks or a coffee-ground appearance is sometimes observed

Patients are usually not ill-looking or febrile; the baby in the early stage of the disease remains hungry and sucks vigorously after episodes of vomiting

Prolonged delay in diagnosis can lead to dehydration, poor weight gain, malnutrition, metabolic alterations, and lethargy

Parents often report trying several different baby formulas because they (or their physicians) assume vomiting is due to intolerance

Careful physical examination provides a definitive diagnosis for most infants with hypertrophic pyloric stenosis. The diagnosis is easily made if the presenting clinical features are typical, with projectile vomiting, visible peristalsis, and a palpable pyloric tumor. Early in the course of the disease, however, some of the classic signs may be absent.

An enlarged pylorus, classically described as an “olive,” can be palpated in the right upper quadrant or epigastrium of the abdomen in 60-80% of infants.

Assessment of the pylorus requires the following:

The patient must be calm and cooperative; a pacifier or small amount of dextrose water may help

If the stomach is distended, aspiration using a nasogastric tube is necessary

With the infant supine and the examiner on the child’s left side, gently palpate the liver edge near the xiphoid process, then displace the liver superiorly; downward palpation should reveal the pyloric olive just on or to the right of the midline

To be assured of the diagnosis, the physician should be able to roll the pylorus beneath the examining finger

The tumor (mass) is best felt after vomiting or during, or at the end of, feeding

When diagnosis is delayed, the infant may develop severe constipation associated with signs of dehydration, malnutrition, lethargy, and shock.

See Clinical Presentation for more detail.


Serum electrolytes should be measured to document adequacy of fluid resuscitation and correction of electrolyte imbalances before surgical repair. The classic biochemical abnormality in hypertrophic pyloric stenosis is hypochloremic, hypokalemic metabolic alkalosis.


The criterion standard imaging technique for diagnosing hypertrophic pyloric stenosis

Muscle wall thickness 3 mm or greater and pyloric channel length 14 mm or greater are considered abnormal in infants younger than 30 days

Barium upper GI study

Effective when ultrasonography is not diagnostic

Should demonstrate an elongated pylorus with antral indentation from the hypertrophied muscle

May show the “double track” sign when thin tracks of barium are compressed between thickened pyloric mucosa or the “shoulder” sign when barium collects in the dilated prepyloric antrum

After upper GI barium study, irrigating and removing any residual barium from the stomach is advisable to avoid aspiration


Reserved for patients with atypical clinical signs when ultrasonography and UGI studies are nondiagnostic

See Workup for more detail.


Hypertrophic pyloric stenosis is the most common condition requiring surgery in infancy. Correction of an associated fluid and electrolytes disturbances is vital prior to general anesthesia induction.
Surgical repair of hypertrophic pyloric stenosis is fairly straightforward and without many complications. However, properly preparing the infant is vitally important.

Preoperative management

Directed at correcting the fluid deficiency and electrolyte imbalance

Base fluid resuscitation on the infant’s degree of dehydration

Most infants can have their fluid status corrected within 24 hours; however, severely dehydrated children sometimes require several days for correction

If necessary, administer an initial fluid bolus of 10 mL/kg with lactated Ringer solution or 0.45 isotonic sodium chloride solution

Continue IV therapy at an initial rate of 1.25-2 times the normal maintenance rate until adequate fluid status is achieved

Adequate amounts of both chloride and potassium are necessary to correct metabolic alkalosis

Unless renal insufficiency is a concern, initially add 2-4 mEq of KCl per 100 mL of IV fluid

Urine output and serial electrolyte determinations are performed during resuscitation

Correction of serum chloride level to 90 mEq/L or greater is usually adequate to proceed with surgical intervention

Before induction of anesthesia, aspirate the infant’s stomach with a large-caliber suction tube to remove any residual gastric fluid or barium; saline irrigation is occasionally necessary to remove a large quantity of barium

Surgical treatment

Ramstedt pyloromyotomy remains the standard procedure of choice

The usual approach is via a right upper quadrant transverse incision that splits the rectus muscle and fascia

Laparoscopic pyloromyotomy may also be used

Endoscopic pyloromyotomy is a simple procedure and can be performed as an outpatient procedure

Endoscopic balloon dilatation of hypertrophic pyloric stenosis after failed pyloromyotomy can be used

A supraumbilical curvilinear approach has gained popularity with good cosmetic results.

Postoperative management

Continue IV maintenance fluid until the infant is able to tolerate enteral feedings

In most instances, feedings can begin within 8 hours following surgery

Graded feedings can usually be initiated every 3 hours, starting with Pedialyte and progressing to full-strength formula

Schedules that advance the volume of feeds more quickly or those that begin with ad lib feeds are associated with more frequent episodes of vomiting but do not increase morbidity and actually may decrease the time to hospital discharge

Addition of an H2 receptor blocker sometimes can be beneficial

Treat persistent vomiting expectantly because it usually resolves within 1-2 days

Avoid the temptation to repeat ultrasonography or upper GI barium study; these invariably demonstrate a deformed pylorus, and results are difficult to interpret

See Treatment and Medication for more detail.

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